The invention relates to improvements in covers, particularly in connection with bed covers which incorporate at least one flexible layer of a light, insulating material.
Covers, as provided particularly for beds but also for other furniture, should be light and flexible, i.e. pliant, so as to be able to sufficiently adapt to the body, while considering the thermal characteristics regarding ambient temperature, e.g. in particular the bedroom temperature at night, such that a more or less “warm” cover is selected. Accordingly, as a rule, in southern countries, the covers regularly only consist of a wool blanket over a simple sheet, which is supplemented by a second wool blanket or further wool blankets when the ambient temperature is colder. In middle and northern Europe, covers are predominantly used in which one layer of light, insulating material consisting of a quilted cover or a down comforter is entirely enclosed by a cover casing. It is also possible to select between thicker or better insulating layers and thinner layers, so as to take the ambient temperature into account. The following consideration is also true for special forms of covers, in particular also for sleeping bags, which are to be included in the term “cover”.
However, it has been shown that a satisfactory resting or sleeping climate can possibly be obtained therewith only to an insufficient extent. During sleep or rest, the vapour permeability of the cover and the ambient humidity of the air may result, depending on the perspiration of the person lying down, in a general or partial body perspiration which is unpleasant both when feeling cool or warm. Apart therefrom, damp bedclothes are also a health hazard if the person becomes uncovered and a local cooling should accidentally occur.
During the night, human beings sweat out up to approximately 500 ml of water. This water or water vapour must leave the entire bed system so as to avoid moisture accumulation in the space taken up by the sleeper under the covers. Dissipation may either be downwardly through the support system, such as the mattress, or through the cover or lateral openings when the body is not completely surrounded.
It is known that the main portion of moisture must be transported off through the cover. However, the moisture meets with various resistances here, i.e. initially the first layer of the cover casing, then the first layer of the cover ticking, then the filler material, then the second layer of the cover ticking, the second layer of the casing and only then reaches the ambient air. While passing these layers, both a storage of moisture, which must again be transported further and discharged, and a mixture of diffusive and slightly convective transportation takes place. As a whole, however, this constitutes slow, moisture-equalizing processes, each of which quasi including high individual resistances. Last but not least, the development of cover tickings for down or fiber covers as well as covers filled with natural hair or animal hair in the direction of a corresponding down or fiber density, and thus textiles having a high fiber density and fine individual fibers, which naturally have a high density as regards a piercing of the individual filler media, but which clearly also provide reduced air permeation. This leads to a reduction of the overall exchange of air containing moisture, and to a kind of congestion. The consequence is—and this is also shown in studies by different institutes—that a quasi tropical climate is obtained within the space under the cover. The air temperatures roughly range between 30 and 35° C. with a correspondingly high air humidity.